Had quite an education here! All chlorine is just chlorine. It's job is to kill stuff and break down other stuff like suntan lotion. The various forms just add other junk that you may or may not want. Tri-chlor tabs add stabilizer and acid...very good for new gunite, tile or shotcrete pools that are curing as the make the water alkaline and...new water needs stabilzer. But tabs are VERY bad for high stabilizer, low pH pools as they make it worse. Di-Chlor powder is similar to Tri-Chlor. Not as acidic but add just as much stabilizer. Cal-Hypo add calcium. I don't know what lithium adds, or if it's a problem or not. I know what it subtracts: Lots and lots of money from your wallet.